What is the function of parallel RC circuit?

fazan83 · Apr 23, 2007

What is function of parallel RC circuit?
When do we usually use this type of circuit?
Please advise.

Thanks in advance.

Electronica · Apr 23, 2007

parallel rc circuit

Parallel RC is basically used for charging and discharging

Kon Zaw · Apr 23, 2007

parallel rc circuit equation

In parallel RC circuit,
for dc source, C charge directly and rapidly, soon the current flow only through R. Vin=Vout soon.
for ac soruces, it show impedence according to the frequency.
I=V/R+jwCV

this circuit is mostly used in oscillators and tank circutis.
and also found in tunning circuits.

fazan83 · Apr 23, 2007

Re: parallel RC circuit

Kon Zaw said:
In parallel RC circuit,
for dc source, C charge directly and rapidly, soon the current flow only through R. Vin=Vout soon.
for ac soruces, it show impedence according to the frequency.
I=V/R+jwCV

this circuit is mostly used in oscillators and tank circutis.
and also found in tunning circuits.

In case for oscillator use, If we remove the R and let C alone. What will happen? What is it different when we add the R to the C parallelly for biasing the oscillator?

Added after 2 minutes:

Electronica said:
Parallel RC is basically used for charging and discharging

What do you mean by used for charging and discharging?
If can then, can you please describe this briefly on how the charging and discharging happen? Why we need to add R parallel to the C as the C alone also the charging and discharging can happen. Please advise.

I am really beginner in this field.

fsahmed · Apr 23, 2007

Re: parallel RC circuit

R provides control to the rate of charging and discharging, without resistance, the capacitor will charge &/or discharge instantaneously, R limits the current, thereby allowing the charging and discharging to happen gradually, governed by:

Vch=V(1-e^(-t/τ))
Vdch=V(e^(-t/τ))

Where V=system/total/ supply voltage
t= time instance under consideration
τ=Time Constant=R*C
Vch= Capacitor Votage at time t during charging
Vdch=Capacitor Voltage at time t during discharging

It takes 5*τ seconds for a capacitor to charge or discharge fully.

NOTE: In parallel circuits, the charging equation does not apply if the supply voltage is across the terminals of the capacitor, it will charge in approx 0 time, while discharge in accordance with the discharging equation.

Kon Zaw · Apr 23, 2007

Re: parallel RC circuit

when R and C are connected in parallel, C charge from a source (there are self starting oscillators but actually it need something like noise)and discharge through R. this process repeat. RC make a time constant which control the oscillating frequency. if we add R to C, it can generally decrease frequency.

fazan83 · Apr 23, 2007

Re: parallel RC circuit

fsahmed said:
R provides control to the rate of charging and discharging, without resistance, the capacitor will charge &/or discharge instantaneously, R limits the current, thereby allowing the charging and discharging to happen gradually, governed by:

Vch=V(1-e^(-t/τ))
Vdch=V(e^(-t/τ))

Where V=system/total/ supply voltage
t= time instance under consideration
τ=Time Constant=R*C
Vch= Capacitor Votage at time t during charging
Vdch=Capacitor Voltage at time t during discharging

It takes 5*τ seconds for a capacitor to charge or discharge fully.

NOTE: In parallel circuits, the charging equation does not apply if the supply voltage is across the terminals of the capacitor, it will charge in approx 0 time, while discharge in accordance with the discharging equation.

Thanks very much for your explanation.

Added after 53 minutes:

Kon Zaw said:
when R and C are connected in parallel, C charge from a source (there are self starting oscillators but actually it need something like noise)and discharge through R. this process repeat. RC make a time constant which control the oscillating frequency. if we add R to C, it can generally decrease frequency.

Thanks very Much Kon Zaw.

grittinjames · Apr 23, 2007

Re: parallel RC circuit

hi i like to know parrelel r how is going to limit current?

fsahmed said:
R provides control to the rate of charging and discharging, without resistance, the capacitor will charge &/or discharge instantaneously, R limits the current, thereby allowing the charging and discharging to happen gradually, governed by:

Vch=V(1-e^(-t/τ))
Vdch=V(e^(-t/τ))

Where V=system/total/ supply voltage
t= time instance under consideration
τ=Time Constant=R*C
Vch= Capacitor Votage at time t during charging
Vdch=Capacitor Voltage at time t during discharging

It takes 5*τ seconds for a capacitor to charge or discharge fully.

NOTE: In parallel circuits, the charging equation does not apply if the supply voltage is across the terminals of the capacitor, it will charge in approx 0 time, while discharge in accordance with the discharging equation.

fsahmed · Apr 25, 2007

Re: parallel RC circuit

grittinjames said:
hi i like to know parrelel r how is going to limit current?

Like I said in parallel, the R acts while discharging, since the source is removed, the only current path is through the resistor.

wisepie · Apr 26, 2007

Re: parallel RC circuit

How about RC used to reduce dumping problem?

mkiani · May 9, 2007

Re: parallel RC circuit

charging and decharging and filtering

CyberX · May 10, 2007

Re: parallel RC circuit

Also with a rc circuit the current will be 90% out of phase with the voltage. The is no timing phase shift with just the resistor. This is for ac circuits by the way. A parrellel rc circuit uses the voltage as the timing referance. And a simple way to remeber weather current is leading or lagging in the cicuit is ICE and ELI (ICE=Current-Capacitance-Voltage) (ELI=Voltage-Inductance-Current).

rfzheng · May 10, 2007

parallel RC circuit

maybe it could be used as loop compensation

pravin_dwaramwar · May 13, 2007

Re: parallel RC circuit

charging and decharging and filtering applications

What is the function of parallel RC circuit?

fazan83

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